Influence of shear stress on erythrocyte aggregation.

Shear stress is known to induce platelet activation and aggregation. The red blood cell (RBC) aggregation test requires the application of shear stress for the cells to disaggregate for initialization. We tested the hypothesis that applying shear stress may activate platelets, which can influence RBC aggregation. The present study used a commercial microchip-based aggregometer (RheoSCan-AnD300) with a rotating stirrer for RBC disaggregation. Whole blood samples were exposed to different magnitudes of shear stress with various shearing times. As the rotational speed was increased up to 2800 rpm, the RBC aggregation index (AI) of the whole blood increased by up to 30% (p <  0.05), whereas that of the platelet-excluded blood samples did not show any apparent alteration. The AI also increased in proportion with the stirring time. The data suggest that high shear stress affects RBC aggregation through shear-induced platelet aggregation.